Thank you for your interest in my emotional states, and you make a good point. However, I don't think these situations are the same.

In terms of population, the biggest London is 9.1 million people and the 2nd-biggest is under 500,000. Quite a big difference! I think that's why when someone says "London" one can usually reasonably assume they're talking about the one in England, unless otherwise specified (or unless they live near a different one).

The biggest Orange County is 3.1 million and the 2nd-biggest Orange County is 1.4 million, so the difference is not nearly as great. I'd even suggest they're in the same general category of size. In the context of a national/international website, it's far less clear that one of the "Orange County"s is so overwhelmingly what people refer to that its state need not be specified.